5 * Author: Tatu Ylonen <ylo@cs.hut.fi>
7 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
10 * Created: Sat Mar 18 02:40:40 1995 ylo
12 * This file contains code implementing the packet protocol and communication
13 * with the other side. This same code is used both on client and server side.
32 /* This variable contains the file descriptors used for communicating with
33 the other side. connection_in is used for reading; connection_out
34 for writing. These can be the same descriptor, in which case it is
35 assumed to be a socket. */
36 static int connection_in = -1;
37 static int connection_out = -1;
39 /* Cipher type. This value is only used to determine whether to pad the
40 packets with zeroes or random data. */
41 static int cipher_type = SSH_CIPHER_NONE;
43 /* Protocol flags for the remote side. */
44 static unsigned int remote_protocol_flags = 0;
46 /* Encryption context for receiving data. This is only used for decryption. */
47 static CipherContext receive_context;
49 /* Encryption context for sending data. This is only used for encryption. */
50 static CipherContext send_context;
52 /* Buffer for raw input data from the socket. */
55 /* Buffer for raw output data going to the socket. */
58 /* Buffer for the partial outgoing packet being constructed. */
59 static Buffer outgoing_packet;
61 /* Buffer for the incoming packet currently being processed. */
62 static Buffer incoming_packet;
64 /* Scratch buffer for packet compression/decompression. */
65 static Buffer compression_buffer;
67 /* Flag indicating whether packet compression/decompression is enabled. */
68 static int packet_compression = 0;
70 /* default maximum packet size */
71 int max_packet_size = 32768;
73 /* Flag indicating whether this module has been initialized. */
74 static int initialized = 0;
76 /* Set to true if the connection is interactive. */
77 static int interactive_mode = 0;
79 /* Sets the descriptors used for communication. Disables encryption until
80 packet_set_encryption_key is called. */
83 packet_set_connection(int fd_in, int fd_out)
85 connection_in = fd_in;
86 connection_out = fd_out;
87 cipher_type = SSH_CIPHER_NONE;
88 cipher_set_key(&send_context, SSH_CIPHER_NONE, (unsigned char *) "", 0, 1);
89 cipher_set_key(&receive_context, SSH_CIPHER_NONE, (unsigned char *) "", 0, 0);
94 buffer_init(&outgoing_packet);
95 buffer_init(&incoming_packet);
97 /* Kludge: arrange the close function to be called from fatal(). */
98 fatal_add_cleanup((void (*) (void *)) packet_close, NULL);
101 /* Sets the connection into non-blocking mode. */
104 packet_set_nonblocking()
106 /* Set the socket into non-blocking mode. */
107 if (fcntl(connection_in, F_SETFL, O_NONBLOCK) < 0)
108 error("fcntl O_NONBLOCK: %.100s", strerror(errno));
110 if (connection_out != connection_in) {
111 if (fcntl(connection_out, F_SETFL, O_NONBLOCK) < 0)
112 error("fcntl O_NONBLOCK: %.100s", strerror(errno));
116 /* Returns the socket used for reading. */
119 packet_get_connection_in()
121 return connection_in;
124 /* Returns the descriptor used for writing. */
127 packet_get_connection_out()
129 return connection_out;
132 /* Closes the connection and clears and frees internal data structures. */
140 if (connection_in == connection_out) {
141 shutdown(connection_out, SHUT_RDWR);
142 close(connection_out);
144 close(connection_in);
145 close(connection_out);
148 buffer_free(&output);
149 buffer_free(&outgoing_packet);
150 buffer_free(&incoming_packet);
151 if (packet_compression) {
152 buffer_free(&compression_buffer);
153 buffer_compress_uninit();
157 /* Sets remote side protocol flags. */
160 packet_set_protocol_flags(unsigned int protocol_flags)
162 remote_protocol_flags = protocol_flags;
163 channel_set_options((protocol_flags & SSH_PROTOFLAG_HOST_IN_FWD_OPEN) != 0);
166 /* Returns the remote protocol flags set earlier by the above function. */
169 packet_get_protocol_flags()
171 return remote_protocol_flags;
174 /* Starts packet compression from the next packet on in both directions.
175 Level is compression level 1 (fastest) - 9 (slow, best) as in gzip. */
178 packet_start_compression(int level)
180 if (packet_compression)
181 fatal("Compression already enabled.");
182 packet_compression = 1;
183 buffer_init(&compression_buffer);
184 buffer_compress_init(level);
187 /* Encrypts the given number of bytes, copying from src to dest.
188 bytes is known to be a multiple of 8. */
191 packet_encrypt(CipherContext * cc, void *dest, void *src,
194 cipher_encrypt(cc, dest, src, bytes);
197 /* Decrypts the given number of bytes, copying from src to dest.
198 bytes is known to be a multiple of 8. */
201 packet_decrypt(CipherContext * cc, void *dest, void *src,
206 if ((bytes % 8) != 0)
207 fatal("packet_decrypt: bad ciphertext length %d", bytes);
209 /* Cryptographic attack detector for ssh - Modifications for packet.c
210 (C)1998 CORE-SDI, Buenos Aires Argentina Ariel Futoransky(futo@core-sdi.com) */
213 case SSH_CIPHER_NONE:
217 i = detect_attack(src, bytes, NULL);
221 if (i == DEATTACK_DETECTED)
222 packet_disconnect("crc32 compensation attack: network attack detected");
224 cipher_decrypt(cc, dest, src, bytes);
227 /* Causes any further packets to be encrypted using the given key. The same
228 key is used for both sending and reception. However, both directions
229 are encrypted independently of each other. */
232 packet_set_encryption_key(const unsigned char *key, unsigned int keylen,
235 /* All other ciphers use the same key in both directions for now. */
236 cipher_set_key(&receive_context, cipher, key, keylen, 0);
237 cipher_set_key(&send_context, cipher, key, keylen, 1);
240 /* Starts constructing a packet to send. */
243 packet_start(int type)
247 buffer_clear(&outgoing_packet);
250 buffer_append(&outgoing_packet, buf, 9);
253 /* Appends a character to the packet data. */
256 packet_put_char(int value)
259 buffer_append(&outgoing_packet, &ch, 1);
262 /* Appends an integer to the packet data. */
265 packet_put_int(unsigned int value)
267 buffer_put_int(&outgoing_packet, value);
270 /* Appends a string to packet data. */
273 packet_put_string(const char *buf, unsigned int len)
275 buffer_put_string(&outgoing_packet, buf, len);
278 /* Appends an arbitrary precision integer to packet data. */
281 packet_put_bignum(BIGNUM * value)
283 buffer_put_bignum(&outgoing_packet, value);
286 /* Finalizes and sends the packet. If the encryption key has been set,
287 encrypts the packet before sending. */
294 unsigned int checksum;
297 /* If using packet compression, compress the payload of the
299 if (packet_compression) {
300 buffer_clear(&compression_buffer);
302 buffer_consume(&outgoing_packet, 8);
304 buffer_append(&compression_buffer, "\0\0\0\0\0\0\0\0", 8);
305 buffer_compress(&outgoing_packet, &compression_buffer);
306 buffer_clear(&outgoing_packet);
307 buffer_append(&outgoing_packet, buffer_ptr(&compression_buffer),
308 buffer_len(&compression_buffer));
310 /* Compute packet length without padding (add checksum, remove padding). */
311 len = buffer_len(&outgoing_packet) + 4 - 8;
313 /* Insert padding. */
314 padding = 8 - len % 8;
315 if (cipher_type != SSH_CIPHER_NONE) {
316 cp = buffer_ptr(&outgoing_packet);
317 for (i = 0; i < padding; i++) {
320 cp[7 - i] = rand & 0xff;
324 buffer_consume(&outgoing_packet, 8 - padding);
326 /* Add check bytes. */
327 checksum = crc32((unsigned char *) buffer_ptr(&outgoing_packet),
328 buffer_len(&outgoing_packet));
329 PUT_32BIT(buf, checksum);
330 buffer_append(&outgoing_packet, buf, 4);
333 fprintf(stderr, "packet_send plain: ");
334 buffer_dump(&outgoing_packet);
337 /* Append to output. */
339 buffer_append(&output, buf, 4);
340 buffer_append_space(&output, &cp, buffer_len(&outgoing_packet));
341 packet_encrypt(&send_context, cp, buffer_ptr(&outgoing_packet),
342 buffer_len(&outgoing_packet));
345 fprintf(stderr, "encrypted: ");
346 buffer_dump(&output);
349 buffer_clear(&outgoing_packet);
351 /* Note that the packet is now only buffered in output. It won\'t
352 be actually sent until packet_write_wait or packet_write_poll
356 /* Waits until a packet has been received, and returns its type. Note that
357 no other data is processed until this returns, so this function should
358 not be used during the interactive session. */
361 packet_read(int *payload_len_ptr)
367 /* Since we are blocking, ensure that all written packets have been sent. */
370 /* Stay in the loop until we have received a complete packet. */
372 /* Try to read a packet from the buffer. */
373 type = packet_read_poll(payload_len_ptr);
374 if (type == SSH_SMSG_SUCCESS
375 || type == SSH_SMSG_FAILURE
376 || type == SSH_CMSG_EOF
377 || type == SSH_CMSG_EXIT_CONFIRMATION)
378 packet_integrity_check(*payload_len_ptr, 0, type);
379 /* If we got a packet, return it. */
380 if (type != SSH_MSG_NONE)
382 /* Otherwise, wait for some data to arrive, add it to the
383 buffer, and try again. */
385 FD_SET(connection_in, &set);
386 /* Wait for some data to arrive. */
387 select(connection_in + 1, &set, NULL, NULL, NULL);
388 /* Read data from the socket. */
389 len = read(connection_in, buf, sizeof(buf));
391 fatal("Connection closed by %.200s", get_remote_ipaddr());
393 fatal("Read from socket failed: %.100s", strerror(errno));
394 /* Append it to the buffer. */
395 packet_process_incoming(buf, len);
400 /* Waits until a packet has been received, verifies that its type matches
401 that given, and gives a fatal error and exits if there is a mismatch. */
404 packet_read_expect(int *payload_len_ptr, int expected_type)
408 type = packet_read(payload_len_ptr);
409 if (type != expected_type)
410 packet_disconnect("Protocol error: expected packet type %d, got %d",
411 expected_type, type);
414 /* Checks if a full packet is available in the data received so far via
415 * packet_process_incoming. If so, reads the packet; otherwise returns
416 * SSH_MSG_NONE. This does not wait for data from the connection.
418 * SSH_MSG_DISCONNECT is handled specially here. Also,
419 * SSH_MSG_IGNORE messages are skipped by this function and are never returned
422 * The returned payload_len does include space consumed by:
430 packet_read_poll(int *payload_len_ptr)
432 unsigned int len, padded_len;
435 unsigned int checksum, stored_checksum;
439 /* Check if input size is less than minimum packet size. */
440 if (buffer_len(&input) < 4 + 8)
442 /* Get length of incoming packet. */
443 ucp = (unsigned char *) buffer_ptr(&input);
444 len = GET_32BIT(ucp);
445 if (len < 1 + 2 + 2 || len > 256 * 1024)
446 packet_disconnect("Bad packet length %d.", len);
447 padded_len = (len + 8) & ~7;
449 /* Check if the packet has been entirely received. */
450 if (buffer_len(&input) < 4 + padded_len)
453 /* The entire packet is in buffer. */
455 /* Consume packet length. */
456 buffer_consume(&input, 4);
458 /* Copy data to incoming_packet. */
459 buffer_clear(&incoming_packet);
460 buffer_append_space(&incoming_packet, &cp, padded_len);
461 packet_decrypt(&receive_context, cp, buffer_ptr(&input), padded_len);
462 buffer_consume(&input, padded_len);
465 fprintf(stderr, "read_poll plain: ");
466 buffer_dump(&incoming_packet);
469 /* Compute packet checksum. */
470 checksum = crc32((unsigned char *) buffer_ptr(&incoming_packet),
471 buffer_len(&incoming_packet) - 4);
474 buffer_consume(&incoming_packet, 8 - len % 8);
476 /* Test check bytes. */
478 if (len != buffer_len(&incoming_packet))
479 packet_disconnect("packet_read_poll: len %d != buffer_len %d.",
480 len, buffer_len(&incoming_packet));
482 ucp = (unsigned char *) buffer_ptr(&incoming_packet) + len - 4;
483 stored_checksum = GET_32BIT(ucp);
484 if (checksum != stored_checksum)
485 packet_disconnect("Corrupted check bytes on input.");
486 buffer_consume_end(&incoming_packet, 4);
488 /* If using packet compression, decompress the packet. */
489 if (packet_compression) {
490 buffer_clear(&compression_buffer);
491 buffer_uncompress(&incoming_packet, &compression_buffer);
492 buffer_clear(&incoming_packet);
493 buffer_append(&incoming_packet, buffer_ptr(&compression_buffer),
494 buffer_len(&compression_buffer));
496 /* Get packet type. */
497 buffer_get(&incoming_packet, &buf[0], 1);
499 /* Return length of payload (without type field). */
500 *payload_len_ptr = buffer_len(&incoming_packet);
502 /* Handle disconnect message. */
503 if ((unsigned char) buf[0] == SSH_MSG_DISCONNECT)
504 fatal("Received disconnect: %.900s", packet_get_string(NULL));
506 /* Ignore ignore messages. */
507 if ((unsigned char) buf[0] == SSH_MSG_IGNORE)
510 /* Send debug messages as debugging output. */
511 if ((unsigned char) buf[0] == SSH_MSG_DEBUG) {
512 debug("Remote: %.900s", packet_get_string(NULL));
516 return (unsigned char) buf[0];
519 /* Buffers the given amount of input characters. This is intended to be
520 used together with packet_read_poll. */
523 packet_process_incoming(const char *buf, unsigned int len)
525 buffer_append(&input, buf, len);
528 /* Returns a character from the packet. */
534 buffer_get(&incoming_packet, &ch, 1);
535 return (unsigned char) ch;
538 /* Returns an integer from the packet data. */
543 return buffer_get_int(&incoming_packet);
546 /* Returns an arbitrary precision integer from the packet data. The integer
547 must have been initialized before this call. */
550 packet_get_bignum(BIGNUM * value, int *length_ptr)
552 *length_ptr = buffer_get_bignum(&incoming_packet, value);
555 /* Returns a string from the packet data. The string is allocated using
556 xmalloc; it is the responsibility of the calling program to free it when
557 no longer needed. The length_ptr argument may be NULL, or point to an
558 integer into which the length of the string is stored. */
562 packet_get_string(unsigned int *length_ptr)
564 return buffer_get_string(&incoming_packet, length_ptr);
567 /* Sends a diagnostic message from the server to the client. This message
568 can be sent at any time (but not while constructing another message).
569 The message is printed immediately, but only if the client is being
570 executed in verbose mode. These messages are primarily intended to
571 ease debugging authentication problems. The length of the formatted
572 message must not exceed 1024 bytes. This will automatically call
573 packet_write_wait. */
576 packet_send_debug(const char *fmt,...)
582 vsnprintf(buf, sizeof(buf), fmt, args);
585 packet_start(SSH_MSG_DEBUG);
586 packet_put_string(buf, strlen(buf));
591 /* Logs the error plus constructs and sends a disconnect
592 packet, closes the connection, and exits. This function never returns.
593 The error message should not contain a newline. The length of the
594 formatted message must not exceed 1024 bytes. */
597 packet_disconnect(const char *fmt,...)
601 static int disconnecting = 0;
602 if (disconnecting) /* Guard against recursive invocations. */
603 fatal("packet_disconnect called recursively.");
606 /* Format the message. Note that the caller must make sure the
607 message is of limited size. */
609 vsnprintf(buf, sizeof(buf), fmt, args);
612 /* Send the disconnect message to the other side, and wait for it to get sent. */
613 packet_start(SSH_MSG_DISCONNECT);
614 packet_put_string(buf, strlen(buf));
618 /* Stop listening for connections. */
619 channel_stop_listening();
621 /* Close the connection. */
624 /* Display the error locally and exit. */
625 fatal("Disconnecting: %.100s", buf);
628 /* Checks if there is any buffered output, and tries to write some of the
634 int len = buffer_len(&output);
636 len = write(connection_out, buffer_ptr(&output), len);
641 fatal("Write failed: %.100s", strerror(errno));
643 buffer_consume(&output, len);
647 /* Calls packet_write_poll repeatedly until all pending output data has
654 while (packet_have_data_to_write()) {
657 FD_SET(connection_out, &set);
658 select(connection_out + 1, NULL, &set, NULL, NULL);
663 /* Returns true if there is buffered data to write to the connection. */
666 packet_have_data_to_write()
668 return buffer_len(&output) != 0;
671 /* Returns true if there is not too much data to write to the connection. */
674 packet_not_very_much_data_to_write()
676 if (interactive_mode)
677 return buffer_len(&output) < 16384;
679 return buffer_len(&output) < 128 * 1024;
682 /* Informs that the current session is interactive. Sets IP flags for that. */
685 packet_set_interactive(int interactive, int keepalives)
689 /* Record that we are in interactive mode. */
690 interactive_mode = interactive;
692 /* Only set socket options if using a socket (as indicated by the
693 descriptors being the same). */
694 if (connection_in != connection_out)
698 /* Set keepalives if requested. */
699 if (setsockopt(connection_in, SOL_SOCKET, SO_KEEPALIVE, (void *) &on,
701 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
704 /* Set IP options for an interactive connection. Use
705 IPTOS_LOWDELAY and TCP_NODELAY. */
706 int lowdelay = IPTOS_LOWDELAY;
707 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &lowdelay,
708 sizeof(lowdelay)) < 0)
709 error("setsockopt IPTOS_LOWDELAY: %.100s", strerror(errno));
710 if (setsockopt(connection_in, IPPROTO_TCP, TCP_NODELAY, (void *) &on,
712 error("setsockopt TCP_NODELAY: %.100s", strerror(errno));
714 /* Set IP options for a non-interactive connection. Use
716 int throughput = IPTOS_THROUGHPUT;
717 if (setsockopt(connection_in, IPPROTO_IP, IP_TOS, (void *) &throughput,
718 sizeof(throughput)) < 0)
719 error("setsockopt IPTOS_THROUGHPUT: %.100s", strerror(errno));
723 /* Returns true if the current connection is interactive. */
726 packet_is_interactive()
728 return interactive_mode;
732 packet_set_maxsize(int s)
734 static int called = 0;
736 log("packet_set_maxsize: called twice: old %d new %d", max_packet_size, s);
739 if (s < 4 * 1024 || s > 1024 * 1024) {
740 log("packet_set_maxsize: bad size %d", s);
743 log("packet_set_maxsize: setting to %d", s);